Metal heater



g. 21, 1934.- E'. BQRNAQD ET AL 1,971,025

METAL HEATER Filed Feb. 10. 1932 Patented Aug. 21, 1934 METAL HEATER Emilien Bornand and Hans Arnold Schlaepfcr, Geneva, Switzerland Application February 10, 1932, Serial No. 592,078 In Switzerland February 16, 1931 2 Claims.

The present invention relates to metal casting and particularly to casting of steel ingots and its object is the provision of an electric heater for insertion into the upper portion of the molten metal cast in the ingot mold for controlling the cooling of the ingot in order to prevent piping.

In our application Serial No. 514,582 filed February 9th 1931, a heater for use with ingot molds is described, which is formed by a refractory plunger body constituting an electric resistor and adapted for insertion into the mold, means being provided on the refractory body to connect the same to an electric circuit which includes the metal cast in the mold so that this circuit is closed when the body is inserted into the metal in the mold. Before the refractory plunger body can be inserted into the cast metal it is necessary to heat the same in order to raise its temperature to the neighborhood of that of the molten metal. It is 20 a primary object of the present invention to provide means for conveniently heating the plunger body previous to its insertion into the molten metal.

The invention will be more fully described with reference to the accompanying drawing, in which,

Figure 1 is a plan view of a plunger body accordmg to the invention.

Figure 2 is a section along the line II-II of Fig. 1.

Figure 3 is a section through an ingot mold with the plunger body in operating position.

The plunger body, made of a refractory pyroconducting material, that means a material which is electrically insulating at ordinary temperature and becomes conducting at high temperature, as for example magnesia, is provided with two cavities l and 2 limiting between themselves a wall 3 and destined to be filled with a liquid metal; two current supply terminals 4 and 5 are insulatedly mounted on top of the plunger body and arranged for connection with the two poles of a source of electric current. Each one of the two terminals is connected to an electrode 6 penetrating into the cavities l and 2 until near the bottom of the cavi- 45 ties.

As it has been explained in our said prior application, the plunger body is destined to be heated, then to be introduced into the molten metal poured into the mold, this in order to prevent the 50 too rapid cooling of the upper portions of the liquid metal, which cooling produces piping of the solidified metal as is well known in the art. The heating of the plunger body, before its introduction into the mold bath, can be made in different 5 manners and particularly, it may be indicated to heat it by means of an electric current. In this case the two cavities are filled with molten metal, for instance with metal coming from the same melt as that poured into the mold, and then the terminals 4 and 5 are connected each one to one of the poles of a source of current.

The liquid metal poured into the cavities 1 and 2 heats the wall 3 to such a degree that this wall becomes conducting. The current can then pass from one of the electrodes 6 through the liquid metal and through the wall 3 to the other electrode. Owing to the resistance which the material of the wall 3 opposes to the passage of electric current, this wall becomes heated to a high degree and transmits its heat to the other portions of the plunger body.

When the plunger body is now inserted into the molten metal in the mold 7 as shown in Fig.

3, the hot walls of the body transmit heat to the surrounding metal and prevent thereby that the upper portion of the ingot cools more rapidly than the lower portions. When the plunger body is inserted into the mold, the terminals 4 and 5 will normally be disconnected from the source of current, but when one works in series and when one has to lower the same plunger body successively into several molds, one can maintain it at the desired temperature, between two consecutive insertions, by connecting again the terminals 4 and 5 to the source.

When the plunger body is inserted in the metal one can also maintain it at the desired temperature by leaving the source of electricity connected to the terminal 4 and 5. However, it will be preferable, in general, to connect one of the poles of this source to the metal in the mold itself, and the other pole to a special terminal fixed to the upper part of the plunger body or simultaneously to both terminals 4 and 5, so that the current is forced to pass through almost the entire cross section of the bottom of the plunger body.

We claim:

1. An electric heater for regulating solidification of molten metal cast in a mold, comprising a heating body adapted for immersion into the molten metal in the mold and consisting of a refractory electric resistance material becoming conductive at high temperature, said body being provided with two cavities adapted to be filled with a hot electrically well conducting liquid for preheating said body, a wall also consisting of said refractory electric resistance material separating the two cavities, electrodes extending into said cavities, and means for con- 1'10 necting the electrodes in circuit with a source of electric current, whereby the circuit will be closed upon hot liquid being filled into the cavities and a current will flow from the liquid in one cavity across said wall to the liquid in the other cavity to thereby raise the temperature of said wall to a high degree.

2. An electric heater for regulating solidification of molten metal cast in a mold, comprising a refractory heating body adapted for immersion into the molten metal in the mold, said heating body being provided with two cavities adapted to be filled with an electrically conduct- 

